How to transition into different ideas?

I have a problem that I hope is common with new composers. I don't know how to get out of a style/texture, then try to change it. Any tips and tricks to make the transition more seamless? This is what I have for right now. It seems I can make the music but I can't glue it together to make one large picture.

A early trick composers are taught is to, before the introduction of another section, have an aspect of it in some other "unimportant" voice, that moves through the transitional cadence to make the next section's material sound related and more sequential. 

That's very good! what @Monarcheon says. Anticipate some material.

I see you have a change of sections aprox. in 00:42, ending in Gm and beginning again in Gm.

I think you can improve the cadence. Making a good spot of rest allows to hear better what comes next. To reinforce the cadence you can make many things: increase the harmonic rhythm, put a rest somewhere, ritardando, etc....

Opposite to this, you can link one part to another. In this case, write a short "codetta" for the first part that harmonically goes to the next. Obviously with a sort of predominant-dominant progression. Put your imagination at work. Use here dis7 chords, or augmented sixth progressions... That would bring color to the music.

I have the same problem. I have a TON of different ideas -but most of the ideas are not consistent with earlier tempo. 

That's a very interesting topic. Anticipating music ideas is a good way to link different parts.

Also a silence or a well placed pedal can be the perfect link beetwen parts, I find very elegant and effective.

As an exemple it's used by F. Schubert in his Unfinished Symphony.
The long pedal (about min 1:12) has a double function of modulating from Bm to GM and introducing a new music idea and section.
The D pedal on Bassons and Horns works perfectly as a common note beetwen the two chords Bm and GM, and as a musical breath preparing the new section.

Thank you all! I am in school so sorry for a long response.

Introducing new material while the old one still going sounds like a plan for me.

I'll give you an update when I get around to doing it.

I'm a little focused on school, apparently Statistics is hard.

You might study your favorite composers to see how they do it. Whom do you admire?

@Morivou_I admire Bach's music, Especially the St. John's Passion.

Mozart would be my #2, The Requiem in D minor.

Luckly scores for these are common on YouTube.